The present novel invention relates generally to a thermal printer adapted to more efficiently print a thermal hard copy output resulting in less time to produce a thermal print. More specifically, the present invention relates to a thermal printing mechanism and method of utilizing a bilateral single head printer or multiple heads for printing alternate or multiple rows simultaneously in multiple colors.
Technology related to the novel invention is disclosed in Japan Patent No. 8,072,282 assigned to Fuji. Also, U.S. Pat. No. 5,367,321 assigned to Kyocera, discloses an electrical circuit system comparable to that used in the novel improved invention. The problem of improving print speed in related printers is addressed in both Japan Patent No. 6,127,267 assigned to Sharp and U.S. Pat. No. 4,774,529 assigned to Xerox. Of further background relevance are Japan Patent No. 7,214,870 assigned to Brother Kogyo; U.S. Pat. No. 5,196,864 assigned to Eastman Kodak; and, Japan Patent No. 7,184,410 assigned to Silver Seiko.
More relevant is Japan Patent No. 8,072,282 which discloses the use of three staggered print heads arranged linearly to improve print speed and Japan Patent No. 6,127,267 wherein two parallel electrodes provide simultaneous recording. Japan Patent No. 7,214,870 also discloses an arrangement wherein one or more print heads are arranged in parallel.
For additional background purposes, U.S. Pat. No. 5,367,321 issued to Shigenori, et al. discloses multiple insulating substrates to form a linear heating element in a thermal printer and U.S. Pat. No. 4,774,529 suggests a printing system for increasing the speed of a multi-color printer when utilized in a single color mode by repositioning the recording head cartridge from a first level to a second level to enable two lines of information to be created during a single scanning pass when it has been determined by the electronic means to be of the same color.
Other art appears in U.S. Pat. No. 5,196,864 wherein a multiple print head thermal printer is disclosed.
U.S. Pat. No. 4,946,297; U.S. Pat. No. 5,000,595; and, Japan Patent No. 7,184,410 refer to the use of four separate line print heads being mounted and teaches how to split a line into four prints using four separate print heads and then joining the line together.
Today""s thermal printers are designed with one thermal head and multiple donor media types. Typically, the donor media is composed of multiple areas of different donor material which are mechanically linked in a specific sequential order. Typically, three areas of color specific donor material are required for a photographic quality thermal hard copy print. For a typical donor today, that sequence of color specific donor material may be yellow, magenta, and cyan. Other donor materials may be composed of a base sequence of four color specific donor areas: yellow, magenta, cyan, and black. The particular sequence of donor material (whatever that may be) is repeated in a serial fashion to complete a roll of donor material.
Referring to prior art, FIG. 1, in producing a thermal hard copy output, donor material (usually the least thermally active color, yellow 15) is positioned over the thermal paper 13. Mechanical rollers 16 and 17, edge and color sensors are used to recognize and position the desired donor material color over the thermal output paper. A thermal head 11, in which pixels 12 (typically 300 per inch) are arranged in a linear fashion, is positioned at the edge of the thermal paper. Digitized control data is then applied to each pixel simultaneously (usually pulse modulated) such that a row or line of one color is printed onto the thermal paper. Through stepper motors and mechanics, and control logic, for example, such as disclosed by the electrical circuit system in Kyocera which is adopted and incorporated herein by reference, either the thermal print head or thermal output paper is advanced one line or row and the thermal transfer process is repeated for that row. This whole sequence is repeated until one color is thermally transferred onto one full sheet of desired thermal output paper. The thermal paper is projected, as shown in prior art FIG. 1b, donor material is advanced to the next color area, and the thermal output paper is re-inserted, as shown in prior art FIG. 1c. The entire process is repeated until the next color (for example, magenta 18) in the sequence is transferred onto the thermal output paper. This process is repeated again with donor material advancing to the next color area until all colors of the donor material are transferred or thermally printed onto the thermal output paper. The problem with this process is that it requires a relatively lengthy time period to complete. More particularly, it is time-consuming, mechanically intensive and requires four paper projections for a donor composed of four independent color areas per each thermal print.
The novel invention resolves the problem of lengthy time consumption and four paper projections for a donor composed of three independent color areas for each thermal print. Specifically, the novel invention significantly reduces the required projections and mechanical steps, and thereby the printing time necessary for a thermal printer to produce a thermal print.
An object of this invention is to provide a novel combination of steps in a thermal printer printing process wherein the output paper is retained and thermal printing occurs in a bilateral direction instead of a unilateral direction and wherein the output paper is ejected after the application of each color.
This object is achieved by a novel integration of a preferred embodiment thermal printer mechanism having a donor media which contains a yellow media section, a magenta media section, a cyan media section, and a black media section, all of which are positioned mechanically between the thermal print head and the thermal output media by the rotation of two roller spools. In addition, the thermal print head contains a mounting mechanism that works like a universal socket wherein the thermal head is precisely positioned over the donor media at the correct angle when the head is traveling in a left to right motion as well as a right to left motion. The stepper motor control is adapted to direct a bi-directional stepper motor and comprises the electronics therefor.
One of the most outstanding advantages of the present invention is that the use of the above described mechanical and electrical combination significantly increases the printing speed of thermal head printers approximately 30% or more.